Curling iron



FIG. 1 is a perspective view of a new, original and ornamental design for a curling iron;

FIG. 2 is a front elevation of FIG. 1;

FIG. 3 is a rear elevation view of FIG. 1;

FIG. 4 is a left side elevation view of FIG. 1;

FIG. 5 is a right side elevation view of FIG. 1;

FIG. 6 is a top plan view of FIG. 1; and,

FIG. 7 is a bottom plan view of FIG. 1.

The broken lines in the drawings depict portions of the curling iron that form no part of the claimed design. 

CLAIM The ornamental design for a curling iron, as shown and described. 